[ARC5] Request for help, aligning BC-453-B.

[Brian]

Hello Les,

When I first started into alignment of superhet radios, I was taught that 
after aligning the IF strip, you always start at the high frequency end. 
Adjust the  trimmers and then the padders. You cannot get at the slugs in 
the Command coil sets. So, you can only work on variable padders and 
trimmers. As I recall, this was exactly the same procedure we taught 
communications students at TAFE. And yes, I know this is almost exactly the 
same as what NAVWEPS 60 etc says. If you treat alignment as an iterative 
process, then you will go back and forth several times till you get the set 
to a state you can accept.

With the BC-453, R-23 and the ARA sets, it doesn't matter if the tit on the 
tuning dial boss is missing. You should wind the variable capacitor to 
maximum capacity, lightly tighten the nut holding the tuning dial with the 
fiducial slightly to the left of the 190 kcs or 0.19 mcs  tuning mark - 
measure the offset. Then traverse the tuning capacitor to the other end and 
observe how far past the 550 kcs or 0.55 mcs mark you have gone - measure 
the offset. If the two measures of offsets are not equal, loosen the tuning 
dial nut and move the dial till the offsets are approximately equal. Now you 
can proceed with alignment of the tuning, using an AF-modulated RF 
oscillator; depending on the particular set (some have a more sophisticated 
AVC than others) you may want to disable the AVC and measure output on an AF 
level meter. If you want to be really clever, you will finally adjust the 
tracking fingers on the variable capacitor movable vanes till you get the 
best tracking, as evidenced by approximately equal output across the whole 
reception range. Tracking can be quite tricky. But if you have 'constructed' 
a set from a kit of disparate parts, you really have no choice. The best 
tracking will be achieved by starting just before the local oscillator and 
ending up at the antenna terminal last.

If you can't get proper spread across the whole tuning range, check the fat 
fixed padding capacitor on the oscillator end of the tuning capacitor.

73 de Brian, VK2GCE.

On Wednesday, January 28, 2015 7:26 PM , Les asked:

I wish to align the front end in my BC-453-B

DOCUMENTATION.
The procedure for aligning is described in the document NAVWEPS
16-30ARC5-501
I put a copy of this document in Yahoo Groups, Files, ARC-5 Articles &
Refs.

The file name is:  ARC-5_Test & Alignment, NAVWEPS_60-30.pdf  (My name
for above).
See section 3 for detail.

I include one page from that document, with extra info I added:
It's called:  "ARC-5, Alignment info sheet.jpg"
It's in the same folder.  That sheet shows the physical location of each
adjustment point.  I added a table showing the specific frequency where
an adjustment can be made.

On the ARC-5 Yahoo group site, you have access to the info I'm using.

SETTING THE MAIN DIAL.
The "pip" on the main dial was broken, so the in first step I set the
sig gen to 500kHz, and tightened the nut holding the main dial.  Maybe I
should have done that at 200kHz, not 500kHz?

ALIGNMENT.
According to these documents, I align C4E at 520kHz (that worked)
At the low end of the band I touch C-9 at 210kHz.  (Here is my trouble.)
      <--- TROUBLE HERE --<

Here is the problem.  I always understand alignment touched 'caps' at
the high end of the band, and coils at the low end of the band.  That's
not what this book says.  It says trim C-9 at 210kHz.  OK, When I swing
C-9 from max to min pFs, I change the frequency very little.  If I set
the '453 dial to 200kHz, my signal generator reads 191kHz.  In other
words, at the low end I'm almost 10 kHz 'off'.

Maybe I should have set the dial at the 'bottom' end (200kHz) and then
trimmed at the top end of the dial?

Any help welcome.
Or, stated more precisely, help!

Les
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